The author meant well. However the issue I took as the daughter of a Borderline is that the strategies suggested, when I described them to my own therapist at the time, she remarked "hmmm, this may well work, but you shouldn't have to play therapist to your mom."
That is exactly what this book, well-meaning though it is, will instruct you to do. Try not to trigger the borderline by constantly validating him and his fragile feelings/ego so as not to trigger a rage attack-not too different from what we nons already suffer through as is. These strategies may well work, but as someone who's spent my life being the emotional punching bag of someone with this disorder, I am simply not willing to use therapy techniques to try and sooth someone who is constantly ripping my head off for no reason besides existing. Nice try, but no thanks, that's why we have professionals. Special tip-a hallmark of BPD is they won't go to a therapist in the first place.